Neptune is the farthest planet from the Sun, an ice giant with a deep blue color from methane in its atmosphere. It’s known for extreme winds reaching supersonic speeds and features like the Great Dark Spot.

This chilly planet is about four times the Earth’s diameter, has a rocky core wrapped in icy mantles and a stormy hydrogen-helium atmosphere. It orbits slowly, takin 165 Earth years for one lap, with 14 moons led by retrograde Triton.

Discovery and Namesake

Galileo recorded Neptune as a fixed star during observations with his small telescope in 1612 and 1613. More than 200 years later, the ice giant became the first planet located through mathematical predictions rather than through regular observations of the sky. Because Uranus didn't travel exactly as astronomers expected it to, French mathematician Urbain Joseph Le Verrier proposed the position and mass of a then-unknown planet that could cause the observed changes to Uranus' orbit. Le Verrier sent his predictions to Johann Gottfried Galle at the Berlin Observatory, who found Neptune on his first night of searching in 1846. Seventeen days later, Neptune's largest moon Triton was discovered as well.